Highway traffic speed determination or estimation is important. Speed estimation is often used to determine where and how to deploy limited transportation funding, i.e., so that the busiest (or most congested) roads receive the most attention. Speed estimation can also be used to provide more timely information, such as providing near real-time traffic information to drivers so that they or their navigation systems may determine a best path between two points. Such traffic speed information can be displayed to a user, for example, as colors overlaid on a map of a roadway system on a navigation device. Such use of traffic information can save on time, aggravation, vehicle wear, and fuel usage.
Traffic speed estimation may be based on speed readings provided by sensors, such as in-road sensors operated by a state highway department or department of motor vehicles. Traffic speed estimation may also be based on probe vehicles, e.g., moving cars provided with location-sensing technology such as GPS, that can report in on their locations and speeds.